Ospf Fault Diagnosis And Troubleshooting - 3Com 7700 Configuration Manual

98 C 5: R P
HAPTER OUTING
OSPF Fault Diagnosis
and Troubleshooting
O
ROTOCOL PERATION
1 OSPF has been configured according to the previous procedures, but OSPF on the
router does not run normally.
Troubleshoot locally
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Check whether the protocol between two directly connected routers is
operating normally. The normal sign is the peer state machine between the two
routers reaches the FULL state. (Note: On a broadcast or NBMA network, if the
interfaces for two routers are in the DROther state, the peer state machine for
the two routers is in the 2-way state, instead of the FULL state. The peer state
machine between the DR or BDR and all the other routers is in the FULL state.
Execute the display ospf peer command to view peers.
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Execute the display ospf interface command to view OSPF information in
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the interface.
Execute the ping command to test whether the physical connections and
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the lower level protocol operate normally. If the local router cannot ping the
peer router, it indicates that faults have occurred to the physical link and the
lower level protocol.
If the physical link and the lower layer protocol are normal, check the OSPF
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parameters configured on the interface. The parameters should be the same
parameters configured on the router adjacent to the interface. The same
area ID should be used, and the networks and the masks should also be
consistent. (The P2P or virtually linked segment can have different segments
and masks.)
Insure that the dead timer on the same interface is at least four times the
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value of the hello timer.
If the network type is NBMA, the peer must be manually specified, using the
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peer ip-address command.
If the network type is broadcast or NBMA, there must be at least one
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interface with a priority greater than zero.
If an area is set as the STUB area to which the routers are connected, the
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area on these routers must also be set as a STUB area.
The same interface type should be adopted for the neighboring routers.
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If more than two areas are configured, at least one area should be
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configured as the backbone area with an area ID of 0.
Ensure that the backbone area connects with all other areas.
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The virtual links cannot pass through the STUB area.
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Troubleshooting globally
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If OSPF cannot discover remote routes and OSPF has been configured
according to the previous procedures and you have checked all local
troubleshooting items, verify the following configurations.
If more than two areas are configured on a router, at least one area should
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be configured as the backbone area.
As shown in Figure 8, RTA and RTD are each configured to belong to only
one area, whereas RTB and RTC are both configured to belong to two